The simplest to understand use of the ている-form is to describe actions in progress, such as the actions depicted in the pictures on this page. We make these sentences by attaching the helping verb ‘いる’ to the end of the て-form of the verb.

This question is asking us what we are doing now. We answer with something like this:
今、勉強しています。
（いま、べんきょうしています。）

The simplest to understand use of the ている-form is to describe actions in progress, such as the actions depicted in the pictures on this page. We make these sentences by attaching the helping verb ‘いる’ to the end of the て-form of the verb.

To express that we were doing something, we simply conjugate the helping verb ‘いる’ into the past form—in combination with the て-form of a verb, this implies that an action happened in the past for a period of time.

This question is asking us what we were doing at around eight pm yesterday. We answer with something like this:
昨日の午後八時ごろ晩ご飯を食べています。
（きのうのごご八時ごろばんごはんを食べています。）