Question: Were equal quantities of matter and antimatter formed during the big bang? And if so, how did the 'pockets' of matter that we experience arise? If equal quantities and matter and antimatter were formed, why didn't they just destroy each other?

Marios Kalomenopoulos answered on 9 Jul 2020:

So this is a really good and difficult question – the short answer is we don’t exactly why this asymmetry is there!
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As you say, if we have equal amount of matter & anti-matter (which would be produced in temperature equilibrium in the standard model of the early universe), they would annihilate, so this means that there must be some sort of asymmetry!
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Now, how exactly this arises it’s an unsolved problem – maybe we need to extend our model of the early universe!
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For a more technical account, you can also search “Sakharov conditions for baryogenesis”, which are more detailed conditions that were proposed by Sakharov at the 60s that would be possible to lead to this asymmetry (these conditions don’t solve the problem, they suggest possible WAYS of solving it, but you need to formulate a new theory that leads there)