Hi Renas, ' I have eaten' is a Present Perfect tense, linking the past with the present. It is an action that happened in the past, but gives no time frame, for example: ' I have eaten Octopus'. 'I ate' is a Past Simple tense - it is an action that happened in the past. 'I ate Octopus yesterday' - is still a Past Simple tense, however here you are referring to a past action within a time frame. Hope this helps.

To answer your comment, yes, you can say 'I ate octopus' on its own, but the past time is always understood. Perhaps it was mentioned earlier in the conversation, for example: Did you have a good weekend? Not bad. How about you? Pretty good, actually. We went to that new seafood restaurant. How was it? Nice. I ate octopus. In this conversation, it's clear that we're talking about a finished period of time, even though the phrase 'I ate octupus' comes a long time after the time period is mentioned. This is different from: 1. Have you ever eaten octopus? No. I've never eaten anything like that. I don't like seafood. 2. Have you eaten yet? No, I'm really hungry actually. OK, I'll make you a sandwich. Conversation 1 is about an unfinished time period - in this case, the person's life up until now. Conversation 2 is about a very recent time which is influencing the present. As Vivienne explained, the present perfect is a tense which links the past with the present - in this case, the person hasn't eaten and so he is hungry now.

You can say "I've eaten too much." or "I ate too much."

Examples "I have eaten": "Yeah, I've eaten it, but I didn't like it." I've eaten snake before. Have you?". "I've already eaten lunch, so I'm not hungry". " I have eaten eaten expired two times in the past year. And bot times I got sick!" Examples "I ate": "I ate a sandwich for lunch today" "I ate lots of Sushi when I lived in Japan" "I ate at that new restaurant in town today. It was really good"