There's no denying Square's (NYSE:SQ) momentum recently. In its first quarter, Square's adjusted revenue and adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) jumped 51% and 33% year over year, respectively. Further, it's not just one or two products driving Square's growth. The company is seeing notable growth across gross payment volume (GPV), Square Capital, instant deposit, caviar, invoices, virtual terminal, and other products.

Commentary from management in Square's first-quarter shareholder letter and its earnings call helped provide further insight into the company's strong results recently. Here's a look at three new quotes from Square management to help investors glean more insight into the company's operations.

An employee and customer interact with the two displays included with Square Register.

Image source: Square.

Larger sellers are increasingly important

Since going public in 2015, Square has closely documented its growing traction with larger sellers. But its efforts to win them over stepped up a notch when the company announced its first high-end checkout product, Square Register, late last year. The $999 point-of-sale hardware with two displays and built-in software by Square showed how seriously Square is taking its move upmarket.

In Square's first quarter, management said net adjusted revenue from larger sellers, or sellers generating more than $125,000 in annualized GPV, increased 60% year over year. Further, Square CEO Jack Dorsey noted that the company is deepening its relationships with these important customers:

And finally, as we've grown upmarket, we found that larger businesses, like other sellers, choose Square because they value the cohesion of our ecosystem. More than half of our largest sellers used 2 or more Square products during 2017. This is important because as these sellers use more products, we deepen our relationship with them. And in turn, they drive meaningful growth for Square.

Higher-margin products are paying off

Another driver for Square's business that investors shouldn't overlook is growth in higher-margin products. As Square grows, the company is finding ways to make more money on each transaction. In Square's first quarter, for instance, transaction-based profit as a percentage of GPV increased from 1.07% in the year-ago quarter to 1.09% in the first quarter of 2018.

Management explained drivers for Square's uptick in its transaction-based profit as a percentage of GPV in its first-quarter shareholder letter:

Transaction-based profit continued to benefit from growth in higher-margin products and improvements in our transaction cost profile. GPV from higher-margin products -- Invoices, Virtual Terminal, and eCommerce API payment -- doubled year over year.

It's time to be aggressive with sales and marketing

Since Square's first-quarter revenue came in higher than expected and management raised its revenue guidance for the full year of 2018 yet kept its outlook for adjusted EBITDA the same, one analyst asked management to explain why it is reinvesting all the incremental top-line upside it is seeing.

During Square's first-quarter earnings call, CFO Sarah Friar essentially said it boils down to the incredible growth opportunity the fintech company has in front of it.

"We're in this enviable position, frankly, right now where we have many strong [return on investment] positive investment opportunities available to us," Friar said.

But one particularly notable area of investment Friar highlighted was sales and marketing:

So we continue to see a payback period of around 3 to 4 quarters, so massive efficiency from a sales and marketing perspective. And so we want to go keep putting dollars back to work because, again, we can grow the ecosystem. And we think that, that over the long run is what will really maximize shareholder value...

Management's commentary on its traction with larger sellers, the growth of higher-margin products, and its impressive return on investment as it spends money to grow its business reinforces why investors should expect plenty more strong growth from Square.

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