I have commits in tortoise svn but I don't know how to see the difference between two commits using tortoise svn to see what changes I made. Can anyone help please?
Local changes If you want to see what changes you have made in your working copy, use the explorer context menu and select TortoiseSVN → Diff.
Difference to another branch/tag Hold down the Shift key while you right click on the file. Then select TortoiseSVN → Diff with URL. In the following dialog, specify the URL in the repository with which you want to compare your local file to.
Difference from a previous revision If you want to see the difference between a particular revision and your working copy, use the Revision Log dialog (Tortoise SVN > Show log), select the revision of interest, then select Compare with working copy from the context menu.
If you want to see the difference between the last committed revision and your working copy, just right click on the file. Then select TortoiseSVN → Diff with previous version. This will perform a diff between the revision before the last-commit-date (as recorded in your working copy) and the working BASE. This shows you the last change made to that file to bring it to the state you now see in your working copy. It will not show changes newer than your working copy.
Difference between two previous revisions If you want to see the difference between two revisions which are already committed, use the Revision Log dialog and select the two revisions you want to compare (using the usual Ctrl-modifier). Then select Compare revisions from the context menu.