C# Programmer's Reference 
Comparison Between Properties and Indexers (C# Programming Guide) 
this is taken from Microsoft : https://msdn.microsoft.com/en-us/library/4bsztef7.aspx

Indexers are similar to properties. Except for the differences shown in the following table, all of the rules defined for property accessors apply to indexer accessors as well.

Property Indexer
Allows methods to be called as though they were public data members. Allows methods on an object to be called as though the object is an array.
Accessed through a simple name. Accessed through an index.
Can be a static or an instance member. Must be an instance member.
A get accessor of a property has no parameters. A get accessor of an indexer has the same formal parameter list as the indexer.
A set accessor of a property contains the implicit value parameter. A set accessor of an indexer has the same formal parameter list as the indexer, in addition to the value parameter.