It rained = rained in the past, a simple fact that is not relevant to now; this is the simple past. EX: It rained yesterday. It has rained = it started raining in the past and is relevant to the here and now; this is actually a present tense convention, specifically present perfect. EX: It has rained off-and-on for six hours now. It has been raining = it started to rain in the past and continues to rain in the present and possibly the future; this is the present perfect progressive. EX: It has been raining all week and will most likely continue through the weekend. There is a lot more to tense and aspect, and how to know when to use one over the other, than just this. If you have further questions, please feel free to ask. I hope this helps. Good luck! :)

'It rained' means that at some point in the past started raining and probably finished. 'It has rained' means that it has at present rained and probably has finished the raining. 'it has been raining' means the raining action started at some point in the past and it is still raining.

One advice for you. Forget grammar. Start speaking. Start using the language.

god, that really came out as a wall of text...

Bre!!! ""Since it has been raining, I am wet." (You can also say: "I am wet because it has been raining.") This new example clearly means that it is currently raining and thus why someone got wet in the present." OK, I was teaching Present Perfect/Continuous and Passive today, so this is really grinding me! Your example simply does not mean that is still definitely raining now! 9am I go to work. It rains. I get wet. 9.30 am it stops raining. 10 am I get into my office with wet clothes. Colleague: Why are you wet? Me: It has been raining. Is it still raining now? No. Present perfect/continuous is not simply just about unfinished time. ""Has" is always present, like your first analysis. So, let's put your example into the present tense instead of the past tense: "Since it has been raining, I am wet." (You can also say: "I am wet because it has been raining.") This new example clearly means that it is currently raining and thus why someone got wet in the present." Another example I have lived in England, America and China. Well obviously I'm not living in all 3 countries at the same time right now, am I? Sorry to be so argumentative and pedantic but I am sure I'm right in all of my examples. For you to be right you need added vocabulary such as "since" or "for". It has been raining since 4pm (ok, still raining) It has rained for 4 hours now (ok, still raining) but It has rained all morning (doesn't mean it's necessarily raining now) It has been raining all morning (still doesn't mean it's necessarily raining now)