Context:
After breaking another election promise, they want to determine what the consequences are for the support of the XYZ party. In the last elections, the party had obtained 12.3% of the votes. A sample of 1200 people is taken, with 120 people choosing the XYZ party.

Given table(It's a standard normal table for Z-values, I can't post images I'm sorry):
https://imgur.com/a/2DtVA2Q

Question A)
They want to determine a 90% confidence interval for the percentage of XYZ voters. Which z value should be used here?
Answer A)
5% in each tail -> 5% look up in the table -> z = 1.645 (or 1.64 or 1.65 is also good)

My question here is how does 90% implie a z value of 1.645? I can't see the pattern here.
I don't know how one can determine that 90% means z = 1.645 from the given table. Where do I even need to look?
And 5% in each tail, what does that even mean?

I know common intervals used are 90%-95%-99% which I can just remember. but what if the exam asks for 93%? I want to know how I would define the corresponding Z-value from the given table.

Hope somebody can explain :) Thank you