The ば form is a conditional that means 'if [A], then [B]'. It is used for situations where the result naturally follows from the condition, like general truths, habits, or predictions. For example, if you say '雨が降れば、試合は中止です', you mean that whenever it rains, the game will be cancelled. It works for both concrete and hypothetical situations, but it is not used for polite requests or invitations (for that, use たら).

To make ば, for verbs you take the dictionary form and change the final u-sound to the e-sound, then add ば. For i-adjectives, you change the final い to ければ. For nouns and na-adjectives, you use ならば, but in everyday speech, なら is more common. Note that ば is a bit more formal and is often found in written language or set expressions.