What is herd immunity? How is it achieved?

I've been receiving a lot of questions about herd immunity. Herd immunity means that there are enough people in the community with a natural infection or the vaccine that they're immune to the virus and we can break the cycle of transmission within the community. The number that has been quoted for SARS-CoV-2 that at least 70% of the people have to be immune or have to have to for us to reach herd immunity. However, we do not know number one that the 70 is true for SARS-CoV-2 because there has been a lot of back and forth what that number should look like. Let's say it's 70%. So what are the reasons that we're not getting to herd immunity and should we still stick to the idea of herd immunity? The reason is that we have vaccine hesitancy, our kids are not vaccinated, and then there are variants. So will we really need to reach herd immunity or we are going to reach some kind of normality is the discussion right now. So there is goal for herd immunity but there are obviously some roadblocks to get for us