simple or basic
rudimentary - basic
Something ‘rudimentary’ is considered to be imperfectly developed or uncomplex. The term is most commonly used in relation to a person’s skill or competency at a particular thing. To a lesser degree, and more so in a professional context, it is also used to express the very early stage of a process or development. A rarely used form of the word is ‘rudimental’.
Don’t be concerned about using that software. You only need a rudimentary understanding of computers to operate it.
When I first moved to Paris, I found it very difficult to adapt and integrate with my rudimentary French.
Our plans for the new product are still quite rudimentary, but I feel they will develop into something very promising.