In poker, the small blind is the first forced bet that is placed before the cards are dealt. It is positioned to the immediate left of the dealer button (or dealer position). The purpose of the blinds is to ensure that there is some money in the pot to play for on each hand.
The order of betting typically starts with the player to the left of the small blind, who can either call the big blind (match the amount of the big blind), raise, or fold. The small blind is not the first to act in the first round of betting post-flop (after the flop, turn, or river cards are dealt), as the betting action starts with the player to the left of the dealer and continues clockwise around the table.
So, to clarify, the small blind does not bet first in the sense of making a voluntary action choice; it is simply a forced bet that sets the structure for the betting rounds to follow.