Should I buy stocks? Should I hold off? Those are the questions that are probably going through may investors' minds right now. After the big stock market rebound over the last three months, it's understandable that there's uncertainty about what to do next.

The answer to investors' questions boils down to what kinds of stocks are being considered. There are definitely some kinds of stocks to avoid right now. On the other hand, pretty much any time is a good time to buy the stocks of companies with tremendous market potential and significant competitive advantages. With this in mind, buying these three stocks is a brilliant move to make right now.

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1. Alteryx

$49 billion. That's the addressable annual market opportunity for Alteryx (NYSE:AYX) in helping people analyze data more effectively. Will the company really hit that level over the next decade? Probably not. But it doesn't have to do so to still be a huge winner.

Alteryx currently claims only a sliver of that ginormous market. The company's revenue totaled close to $418 million last year. But its sales are growing fast, up 43% year over year in the first quarter even with a slowdown in March due to the COVID-19 pandemic.

Customers love how easy Alteryx's software makes analyzing large amounts of data. No spreadsheets. No programming. And lots of flexibility. It's not surprising that Alteryx now has more than 6,400 customers across every major industry, including 37% of the Global 2000. And existing customers continue to use more of the company's products: Alteryx's net expansion rate in Q1 was 128%.

Gartner named Alteryx as a leader in its 2020 Magic Quadrant for Data Science and Machine Learning Programs and ranked the company No. 1 on the ability to execute. My view is this ability to execute is what especially differentiates Alteryx -- and what will enable it to capture a much larger chunk of its $49 billion per year opportunity.

2. Guardant Health

Liquid biopsy might not be a subject that you talk about every day. However, the blood test that detects cancer by finding DNA fragments of tumor cells could become one of the most important healthcare innovations of our time and save a lot of lives, perhaps even including yours one day. And Guardant Health (NASDAQ:GH) is an early leader in liquid biopsy and a stock that many investors are talking about.

Guardant Health is currently evaluating its LUNAR-2 liquid biopsy assay in a clinical study for the early detection of colorectal cancer. The company estimates that the annual addressable U.S. market for the product totals more than $30 billion. Its LUNAR-1 product, which is being researched for use in cancer recurrence monitoring along with adjuvant therapy and screening, targets an additional annual market opportunity of $15 billion.

In the meantime, Guardant Health already markets two successful liquid biopsy products. Guardant360 is the market leader in helping match people who have advanced-stage cancer with the best therapy. GuardantOmni helps drugmakers screen patients for clinical studies evaluating cancer drugs.

These two current products give Guardant Health plenty of room to run. The U.S. market alone represents a $6 billion per year opportunity. Guardant Health's market cap currently stands at a little over $8 billion.

3. The Trade Desk

Very few growth stocks get me as fired up as The Trade Desk (NASDAQ:TTD). The company appears to be an unstoppable player that is profiting from two unstoppable trends: the simultaneous adoptions of digital advertising and programmatic advertising.

Digital advertising is everywhere. Its growth these days is especially being fueled by connected TV (CTV). Consumers are flocking to connected devices and streaming content. Programmatic advertising uses software for buying and selling ad spots instead of conducting person-to-person negotiations. The two trends go hand-in-hand. The more digital advertising, the greater the need is for programmatic advertising.

The Trade Desk ranks as the clear leader on the buy side of the programmatic advertising market, winning multiple industry awards for its software. Its platform enables ad agencies to quickly and easily buy digital ads that maximize their return on investment. 

With the dramatic growth in CTV and programmatic advertising, I think that The Trade Desk could realistically triple an initial investment over the next 10 years. Any investor can get fired up about that kind of growth opportunity. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.