It's not like that. There are three types of Conditionals and there also are exceptions from the rules. But let's stick to the first rules:
1. Conditional Clause Type 1. - truth, validity:
Main Clause - Future Tense / Conditional Cl. -Present Tense: "I will go out if you join me".
2. Conditional Cl. Type II: possible, desirable actions: Main Clause - Future in the Past / Conditional Cl. - Past Tense: "They would go shopping if they had money." 3. Conditional Cl. Type III: unreal, impossible actions: Main Cl - Future Perfect / Conditional Cl- Past Perfect: "John wouldn't have lied to you unless (=if not) she had believed him from the very beginning."