What do these characters mean è é ë ê?

In English its almost always easy, the letters of the alphabet always come in one form and always pronounced the same. In Arabic, the letters are also the same but the way you pronounce them can come in four different ways per letter depending on a little mark that is put on top of the letter.

What I do not get is the special characters from other European language. 

I know that when you use é -or was it è?- it somehow means eh… like creme brûlée. I however do not understand the û and why would it differ in pronunciations between brûlée or brulee… to me they look identical sans the fancy letter work.

How does è differ from é, ë, or ê? What about the ñ and õ? Why is it that the e and o and a come with all the different variations while the n only comes in one which is ñ? Why isn’t the t or k or f among those that come in different pronunciations? I know I sound like a toddler who keeps asking why but I’m always intrigued and somehow feel a bit, how do I put it? Ignorant. Yes, whenever I come across a word with such variations I am washed by a wave of how ignorant in foreign languages I am and how at that very moment I am faced with a word I cannot pronounce, which irks me. I’ve never been to a private school in Kuwait, I was in a government school and had to learn English on my own to keep up with my siblings who all went to private schools and all my peers who went to college abroad, but its these little things that remind me all the time of what I’ve missed while teaching myself to take my English to another level. I hate not knowing, plain and simple.

So, do all English speaking people know what these special characters mean? I assume they learn about it in school perhaps or something. Am I wrong?