English progressive verb tenses describe ongoing actions in the present, past or future. What’s the difference between each pair of simple tense forms? Not a whole lot unless you are a grammarian. People often interchange present and progressive forms without creating any problems. But shades of difference in meaning do exist.
Present progressive
The present progressive form often implies a process:
Alexei is axing the proposal to cut down the national forest. (is axing is in present progressive form)
Michael and Lulu are skiing far too fast toward that cliff. (are skiing is in present progressive form)
The single-word form of the present tense may be used for things that are generally true at the present time but not necessarily happening right now. For example:
Ollie attends wrestling matches every Sunday.
If you call Ollie on Sunday, you’ll get this annoying message he recorded on his answering machine because he’s at the arena (attends is in present tense). You may also get this message on a Thursday (or on another day) and it is still correct, even though on Thursdays Ollie stays home to play chess. Now read this sentence:
Ollie is playing hide-and-seek with his dog Spot.
This sentence means that right now (is playing is in the progressive form of the present tense), as you write or say this sentence, Ollie is running around the living room looking for Spot, who is easy to find because he ran through that tray of fluorescent paint.
Past progressive
The difference between the plain past tense and the past progressive tense is pretty much the same as in the present tense. The single-word form often shows what happened in the past more generally. The progressive form may pinpoint action or a state of being at a specific time or occurring in the past on a regular basis.
Gulliver went to the store and bought clothes for all his little friends.
This sentence means that at some point in the past Gulliver whipped out his charge card and finished off his Christmas list (went and bought are in past tense).
While Gulliver was shopping, his friends were planning their revenge.
This sentence means that Gulliver shouldn’t have bothered because at the exact moment he was spending his allowance, his friends were deciding what time to pour ink into his lunchbox (was shopping and were planning are in the progressive form of the past tense).
Gulliver was shopping until he was dropping, despite his mother’s strict credit limit.
This sentence refers to one of Gulliver’s bad habits, his tendency to go shopping every spare moment (was shopping and was dropping are in the progressive form of the past tense). The shopping was repeated on a daily basis, over and over again. (Hence, Gulliver’s mom imposed the strict credit limit.)
Future progressive
You won’t find much difference between future and future progressive. The progressive gives you slightly more of a sense of being in the middle of things. For example:
The actor will be playing Hamlet with a great deal of shouting.
The actor's actions in the sentence above may be a little more immediate than
The actor will play Hamlet with a great deal of shouting.
In the first example, will be playing is in the progressive form of the future tense. In the second example, will play is in future tense.