Normally, a creature can block no more than one creature, regardless of power and toughness (C.R. 509.1a). But if an effect (such as Brave the Sands) lets a creature block more than one creature, it can do so regardless of power and toughness. This means, for example, that Brave the Sands lets a "creature you control" block two other creatures regardless of their power and toughness (e.g., a 1/5 "creature you control" can block a 6/2 creature and another creature just fine this way).
Normally, a creature can block no more than one creature, regardless of power and toughness (C.R. 509.1a). But if an effect (such as Brave the Sands) lets a creature block more than one creature, it can do so regardless of power and toughness. This means, for example, that Brave the Sands lets a "creature you control" block two other creatures regardless of their power and toughness (e.g., a 1/5 "creature you control" can block a 6/2 creature and another creature just fine this way).
EDIT (Feb. 19, 2021): Edited.