Serving size??

agree with above. depending on food i eat more or less than 1 serving. my goal is to meet my daily or weekly calorie goal.

this thread has great information on getting started:
https://community.myfitnesspal.com/en/discussion/10300331/most-helpful-posts-getting-started-must-reads#latest

Serving sizes don't really mean a lot-it just gives you the amount of calories/macros and micros per a certain amount of grams. For weight loss you want to make sure your total calories for the day is around your calorie target (what MFP has figured out for you). Within that though, you can chose to eat more or less of foods, in whatever way fits with your preferences, hunger, macros targets etc.

For example-I just had lunch, which had 4 servings worth of vegetables, 2 servings worth of meat and then 1 serving of olive oil and 1 serving of wheat crackers. I chose these amounts based on their calorie makeup, how filling they make me feel, and then their macros makeup, which is something I'm paying attention to right now, (but is secondary to calories).

In a nutshell, eat whatever servings you like with a goal to fit them into your calorie targets

There's no need to stick to the serving size, but it can be helpful when estimating cals (before you log) or making judgments about what number of cals that component will contribute to your meal. A serving size of pasta is about 200 cal, and I tried making that (with some lean protein and lots of veg) and found it quite satisfactory, so I will usually stick to a serving. Same with most other grains, like oats, barley, whatever.

With foods like meat (or other sources of protein) and veg, I focus more on putting together a satisfying meal and also the amount of protein I want. I usually aim for 25-30 g of protein in a meal (but that's me, you may find you prefer getting a lot more in one meal and less in others) and make sure my plate has some volume, usually achieved by making half the plate or more veg.

When I was actively logging and losing (I'm at maintenance), I never thought about serving size at all or learned them, other than packaged stuff (as mentioned above). I did have a sense of how to make up a meal that would hit my protein and calorie goals -- that's something that if you don't have you will learn by logging (or try to prelog some).

If you are hungry, the first thing is to consider whether the calories you are consuming are appropriate -- many start with an overly aggressive goal. After that, think about switching up food choices some or meal timing. I find snacking makes me feel less satisfied, so I don't. Others feel otherwise. I find that protein and veg and fiber more broadly tend to be filling for me (but I need a decent amount of fat to feel satisfied), others have different reactions.

One thing I noticed was there was a period of a few days when I first started when I'd miss food at times I might have snacked (but not really hunger). I would get coffee or tea (black) or eat some raw veg at such times until I got more used to just not eating at all between meals (which again was what has always worked best for me, not saying it's right for all).

The serving size (measured by weight not by x amount of pieces) is what you use to count your calories. You don't need to only eat 4oz of chicken or 33g of protein powder. You can eat however much of whatever you want, as long as the calories equal up to your goals.

Basically...

There is far more to it than that, but as far as weight loss goes, CICO, calories in vs calories out.