The word "algorithm" may sound scary. But you know algorithms from your everyday life. An algorithm is just a list of steps one has take to achieve a goal. If you know how to cook spaghetti, then you know at least one algorithm. The algorithm, the list of instructions, for spaghetti carbonara might look like this:

1. Put a pot of water on the stove.
2. Add salt to the water.
3. Bring the water to a boil.
4. Put the spaghetti in the boiling water.
5. Finely chop 100g of pancetta.
6. ...

You do not only already know many algorithms. You are also able to understand completely new algorithms and, usually, you will be able to apply them. When you read a new recipe, you will most probably be able to cook the described meal. (Unless it contains ingredients which are impossible to get in your region or something like that. But that is unrelated to your algorithm understanding capabilities.)

Most probably you have also seen algorithms that contain conditions: "If your meat doesn't contain a lot of fat, add more butter." If you understand such cooking algorithms, you will also understand trading algorithms. Here is one:

If the price of gold falls three days in a row, buy gold.

Please do not use this algorithm for trading! It has not been tested. We just use it as an example for explaining what algorithms are.

We just said that the above algorithm has not been tested. What does that even mean?