A preterite (/ˈpreˌtəˌraɪt/) is the form of the verb used by itself in the past tense.
Some full modal verbs have preterites too.
The preterite is not used with auxiliary do (preterite: did); rather a bare infinitive is used instead, as a second grammatical marker is not necessary. e.g. "I ate a sandwich" "I did eat a sandwich".