There are a number of characteristics that make something "essential" not just the fact that it is needed by the body, although that is the first. The second is that it must only be available from...
The phrase means that they are essential in the diet, because the body cannot produce them internally from other compounds. It should not be interpreted to mean that they are somehow more important...
essential amino acids are those that we cannot produce while non-essential amino acids are those that we can produce by ourselves by nitrogen containing compounds in our body.