Craftsman CMCS351B V20 reciprocating saw, tool only

Brushless motors use electronic control instead of carbon brushes, which generally means less wear, less heat and more runtime per charge. Brushed motors are simpler and often cheaper, and are fine for lighter or occasional use, though their brushes can wear out over time.

This lists how many batteries come in the box, if any. Tool-only (bare) listings include no battery or charger, which suits buyers already on that battery platform. Two batteries let you charge one while working with the other.

Amp-hours (Ah) is the battery's charge capacity. At the same voltage, a higher Ah pack runs longer between charges but is usually larger and heavier. Smaller packs keep the tool lighter for overhead and light work; larger packs suit saws, grinders and other high-draw tools.

This states whether a charger is included and which type. Chargers vary in output, so the same battery can take noticeably different times to charge on different chargers. Tool-only listings usually include no charger.

This is the maker's published warranty term. Terms for tools, batteries and chargers often differ, and some depend on registration or exclude certain uses. Read the maker's terms for what is covered, how claims are handled and whether proof of purchase is required.