The phrase "to capture a base" means to take control or possession of a specific location that serves as a strategic point in a game, sport, or military situation. Full definition
While you can complete the game without capturing every base on the map, there are advantages to taking over as many of them as you can. (gamerstemple.com)
Also, most robots can turn into a vehicle for quicker movement across the land, but can not capture bases or attack while in this mode. (slidetoplay.com)
During the game you can capture bases which act as safe zones for you to level up, swap characters, craft weapons and generally relax in. (wolfsgamingblog.com)