When an object is changed, it is available to visually compare files containing information about object version on the server and in the local folder.
To compare object versions, select the 
Compare Versions or Compare with the Latest Version item in the changed object's context menu in the object navigator, project navigator or on the Changes tab on Pending Changes panel in the development environment. After executing the operations the application for versions comparison opens.
In Git versions can be compared using the WinMerge application:
Download and install the WinMerge application.
Add the path to the folder with installed WinMerge to the Path variable in the Windows environment variables.
The WinMerge application will be started on object versions comparison:
NOTE. The WinMerge application is also used on resolving conflicts in the Git version control system.
In Team Foundation Server versions are compared using a standard dialog box of version control system:
Select the files to compare and click the OK button. After executing the operations the comparison window opens:
NOTE. Depending on the selected object, the server and the local copy have different number of saved files. By default, files are compared with the text of a unit or a form. In an assembly a file containing the list of units or forms is compared.
See also:
Developing Applications in a Team | Getting Latest Version of Objects | Checking Out Object for Edit