Most all programming environments end up with values or characters which are special in nature. For example, you can't use mathematical operators within the names of your fields. These characters are reserved for an obvious reason.
When creating your solution, there will be solution specific standards beyond those documented here. It is suggested that you create a script named Reserved keywords and add comment script steps for each reserved word within the solution. This facilitates a convenient location to reference when choosing what to name variables and other elements in the solution.