Pseudocode (pronounced SOO-doh-kohd) is a detailed description in plain language (not programming language) of what an algorithm should do. Pseudo- means not true or real, so you could say that pseudocode is fake code, but it's useful for working out what an algorithm should accomplish.
You can also think of pseudocode as a high-level outline. Pseudocode is usually written to plan out a large or complex part of a program before writing real code.