mySAP is not a single product but is a suite of products from SAP including SAP R/3.
SAP R/3 was First launched in 1998 , is regularly updated ,and is market leader in ERP category till date.
SAP R/3 many modules such as HR , Finance , MM covering all enterprise Functions
"3" stands for three tier architecture - Presentation tier , Logic tier and Data tier.
Other products in the mySAP product suite includes SRM(Supplier Relationship Management), CRM(Customer Relationship Management), PLM(Product Lifecycle Management ) , SCM (Supply Chain Management)
Following Video will take you through the SAP product suite.
Click here if the video is not accessible