You contribute to a translation job either by entering new translations or by editing the existing ones. The contributions are measured by the number of edits - each character you enter or revise. The contribution to a job by each user is also shown in percentage format.
To view the jobs your contributed to,
All active jobs that you have worked on and your contributions to them are listed on the page. The active jobs include open or closed ones. You cannot view archived jobs. Note that page is not updated in real time and thus the data might be out of date.
To view contributions given to a job by all users,
You can go further to see the contributions to each segment of the job.
Note: Either new translations or revisions to existing translation are calculated as contribution. Improving existing translation is an important way to earn translation money!