If you want to say, "What I had for breakfast this morning was eggs", then you say, "I had eggs for breakfast." If you wanted to say this, "I have had eggs for breakfast before (I've eaten that at least once in my life)", then you can say, "I've had eggs for breakfast."

the difference is that the first one "I've had eggs for breakfast" is in the present perfect tense and the second "I had eggs for breakfast" is in past simple. That's a pretty basic description though. Essentially the two sentences have meanings that are so close to each other they might as well be the same thing. present perfect simple is used to talk about something that happened in the past with an effect on the present, so your breakfast this morning would count as something that is still having an effect now Example: I've been to China (This happened in the past and is still relevant now) / I've seen lots of marvel films (again this is something that happened in the past and continues to have an effect now) the past simple is an easier way to express this same thing and has essentially the same meaning in simple sentences like this Example: I went to China in 2017 (this happened in the past BUT since i am using the past simple if would be normal to specify a time that it happened, unlike the present perfect simple) / I saw lots of marvel films last year (same thing here, since it's past simple it would be more normal to specify a time when this happened) So the past simple is better at talking about a specific instance (I had eggs for breakfast THIS MORNING) and the present perfect simple is talking about things generally in the past up to now that still have an effect (I've had eggs for breakfast - this is telling me that you have done this before and probably did today, but you haven't actually clearly specified that)

"I've had eggs for breakfast" means you've eaten eggs in the past during breakfast. "I had eggs for breakfast" means you ate eggs for breakfast *today* "I've had breakfast" means you ate breakfast today Example: I'm not hungry because I've had breakfast already. "I had eaten breakfast" is usually used when telling a story in past tense from before today. Example: When I went shopping, I had eaten breakfast beforehand to prevent myself from buying junk food. Hope this helps :)

"I had eggs for breakfast" is the most basic meaning and is probably what you'll hear and use most often. However, "I've had eggs for breakfast" could be used in specific contexts: 1. Life experience - "I've had eggs for breakfast, but I've never had eggs for dinner." 2. A completed action that's part of an ongoing event - "I've already had eggs for breakfast, so I'm going to get some waffles before the breakfast buffet closes."

If you're talking about this morning there's no difference. If you were asked. "What did you have for breakfast ?" you could use either of these replies. The other answers have tried to explain in what types of situation you would use the present perfect 'I've had . . ' This is a difficult tense to learn and maybe the best way to understand how it's used is by looking at examples. Don't get too worried though if you don't get it right. The difference is often quite unimportant.