Equity Investments: Market Organization and Structure

Hello everyone!!
I have a question that is not a doubt particulary for just this topic, but for all securities:

Why does a high spread between the buy and sell price for a security (stock, bond, currency exchange…) means that the security is not liquid?

Is it because as there is few buyers and sellers for that security, the dealer needs to make money by making wider the spread?

Thanks in advance!

Yes.

thank youu!! I really had that doubt but could not find the answer

My pleasure.