The main misconception most of people who are not so familiar with Chinese have is they think the characters are pictures. While it is true for a few characters, they are called characters and not hieroglyphs for a reason: because the vast majority are not pictographic.
Types of characters
There is a lot of information about it on the internet so here we will just sum it all up. These are three major types:
1) Simple Ideograms (指事)
Represent an abstract idea
一二三上下本
2) Compound Ideograms (會意）
Represent an idea based on a combination of ideas
武信林森
3) Phono-semantic compound characters (形聲/諧聲)
This type makes up over 90% of all the characters. It’s easy to see how it works on an example:
媽 — the left part of the character is 女 (nǚ) means female, the right part is 馬 (mǎ) suggests the sound. So what does 媽 mean and how does it sound? The sound is mā, the meaning is mother. So the sound differes in just the tone, this is awesome! There is always one but. It would be naive to expect the pronunciation and the meaning of the characters stay the same over so many years. Which makes a lot of characters from this category mislead you.
Now, the question is how many of the characters preserved the meaning, how many have their meanings altered? There are no exact or approximate numbers, but from my experience I would say 50/50. That to say, the characters that remained the meaning do not give you the meaning explicitly, you might want to look up an etymology dictionary to see the logic behind the components. It’s much worse with the sound, most of the characters you see do not match the sound with their phonetic component.