The original form of a verb is called an ‘infinitive’.
A ‘full infinitive’ has the word ‘to’ before it, e.g. ‘I went to watch the James Bond film’.
A ‘bare infinitive’ does not have the word ‘to’ before it, e.g. ‘You should watch the new James Bond film!’
Sometimes infinitives are called ‘base forms’.
If you have a table of verbs, the ‘infinitive’ column is usually on the left.
With regular verbs, the infinitive normally ends -ed when talking about the past, but other spelling changes are sometimes required.
E.g. I walked into the room.
Sometimes the infinitive will be followed by –ing, (for example in gerunds and continuous tenses),
E.g. I was walking into the room when I tripped over.
Irregular verbs do not normally end -ed in the past.