Internal

• Internal is the default
• Can only be read in the contract they are defined and in derived contracts. If you do not specify visibility for a variable, it is deemed internal. Example ownerAddress is internal variable

address ownerAddress; // default internal

Public

compiler automatically generates getter functions for them.When used within the same contract, the external access (e.g. this.x) invokes the getter while internal access (e.g. x) gets the variable value directly from storage

Private

internal variables not visible in derived contracts