A closer look
Tense in grammar is the form of a verb that shows when an action happened.
I walked to school is past tense; I walk to school is present tense.
The same change shows up in everyday talk. Someone telling you about yesterday says I missed the bus; someone describing today says I miss the bus. Only the verb form changed, and that change is the tense.
You also hear it in questions. Did you eat? asks about the past, while Do you eat fish? asks about habits in general. The helping verb did carries the past tense in the first one.
One small wrinkle: a past form does not always point to the past. If you ask a stranger, Did you want help? you are speaking right now, not about yesterday. The past form just sounds softer and more polite.