Custom dimensions are like dimensions that are already predetermined in the Analytics account, except that they are created by the analyst to study dimensions of their choice. These dimensions can be used to collect and analyze data that web analytics tools do not automatically follow, such as CRM data, phone calls, data about users who register…
Custom dimension in Google Analytics
Custom dimensions can appear as primary dimensions in custom reports, and can also be used as segments and as secondary dimensions in standard reports.
Custom dimensions and metrics allow you to combine Analytics data with data such as CRM. For example, if the gender of users of a CRM is recorded, it can be combined with Analytics data to see which pages each person has viewed according to their gender. These custom dimensions can be displayed as primary dimensions in custom reports. They can also be used as dimensions and child segments in standard reports.