ERP is the abbreviation of Enterprise Resource Planning and it refers to a computer program (software) which consists of several subprograms (modules) that individually support a specific task.
In the past, many companies used several computer programs (isolation of IT resources and data had to be inserted multiple times) to support the different business activities. In an ERP system, a large amount of processes can be accommodated in one single program.
A main advantage of an ERP system is that your data only have to be inserted once, since only one database is required. Additional advantages are that the chance of inconsistent data is reduced and that you can operate more efficiently, which will save money.