Verbs, "doing words", use tenses to show us the time of their action. The present tense is happening now and the past tense has already happened.
Have you ever listened to sports commentary? Often the commentator will be talking in the present tense: "and she passes the ball to Jones....." Later, after the match or during half-time, the commentators will discuss the match using the past tense: "her decision to pass the ball to Jones led to the team's first try..." In the first sentence, the verb "passes" is in the present tense, and in the second, the verb "led" is in the past tense. Pass/passes are present; passed is past tense. Lead/leads are present tense; led is past.
But what about the verb "pass" in the second sentence? It looks like a present tense verb, doesn't it? If you look again, you'll see that the verb here includes the word "to", "to pass". This is an example of an infinitive, which is neither past nor present. You can often find infinitives joined to other verbs, for example: "Hughes decided to pass the ball to Jones, leading to the try." This sentence is also in the past tense. The verb phrase here is "decided to pass", with "decided" indicating the past tense.
If in doubt, have a bash at this quiz on past and present tense verbs.