Often there are several translation options for the same strings. We support upvoting so contributors can decide which option is the best.
Begin by enabling Translation upvoting in project settings (it's turned off by default). Please note, this will automatically enable Reviewing for the project, as reviewing should be used to override the translation version rating.
Once both options are enabled, it is important to give some users reviewer access. Navigate to the project's Contributors page and turn on the reviewer option for users who have the permissions to override the voting by reviewing the translation.
With upvoting enabled, all versions of the translation (ever submitted by contributors) will be displayed in the inline suggestions dropdown menu once you click on the corresponding translation. Users without reviewer access will have the option to upvote or downvote each version or to enter a new one. The number on the right hand side of the up/downvote arrows shows the positive or negative balance of that particular translation entry. Each user can give only one vote (up or down) for each of the translation versions (this applies to versions submitted by other users).
Translation version rating therefore affects which version becomes the "main" one and will be included in project export, however if the translation is reviewed (approved) the rating changes will not affect the "main" translation until the reviewer either removes reviewed flag or reviews another version.