This is a somewhat contested topic, but there’s some simple rules to outline here. A “complete” protein will have a large range of amino acids contained in it, which stimulates muscle growth. This is found in animals and animal products. “Incomplete” proteins are proteins that don’t have a large range of amino acids, and these are generally found in plants and other non-animal based products. Some arguments have been made that if you eat a diverse enough palate that the amino issues of veganism aren’t as detrimental. However, there are simple some aminos you cannot get outside of animal sources. But this does not mean that vegans are doomed to inferiority. It is not nearly that simple.
The tricky part about this conversation is that there is a good amount of science supporting the idea of these categories, but then there are also people like the olympic weightlifter Kendrick Farris who is vegan and eats low amounts of protein. In my opinion, it’s a matter of what side you’d rather err on. I prefer to have enough protein theoretically so that I’m not missing out, other people don’t have that same inclination. It’s up to your own judgement call in the end. I will say that I have personally experienced better results when still eating things like eggs and fish and maintaining upwards of 0.7g protein per 1 lb of body weight. Protein is slightly up in the air, but aminos are fairly important no matter who you are.