Base stats are a little hard to explain. Basically, they're the basis by which any Pokemon of that species has its stats calculated. They play a much stronger role in this calculation than anything you can control by training, so if you look at base stats you can get a good feel for where a given species' strengths and weaknesses will lie.

As some general baselines. 90-100 is fairly good. 110's is a solid strength. 120 or higher is excellent. We're talking 142.

As a point of comparison, 142 base speed makes it about the 11th fastest Pokemon in the whole National Dex (if you count alternate forms, like the Deoxys forms and Mega Evolutions). Removing Pokemon that don't exist in Sword and Shield from the equation, Ninjask, Accelgor, and (potentially) Zacian and Zamazenta are the only things faster than it.