In English each verb has three different forms, which are needed to construct the tenses:
As you can see in the above table, the suffix -ed is added to the base form in order to create the second and third form of regular verbs. However, many of the most frequent verbs are irregular and, therefore, need to be learned by heart. For example:
In order to learn the irregular verbs by heart, the "Table of Irregular Verbs" of the Cambridge Dictionary Online is very useful.