The Options button on the top right opens the options dialog with several settings.
Optimize routes - if disabled, the order of destinations not optimized
Home address - the default departure address that will be added to the map each time
Default departure time - departure time from which arrival times are calculated
Default service time - default service time, used for arrival times and time windows
Geocoding preference - the geocoder service used for finding addresses on the map
Suffix address - suffix added to addresses when send to geocoding service
Check address precise - gives a warning if a geocoding service does not return a precise result, e.g. no street or house number
Map style - select another theme for the map
Retina maps - allow the use of high resolution maps (only on retina screens and when available)
Maps in driving directions - add detailed maps for destinations in the driving directions
Show labels - add text labels for each location to the map next to the marker
Buttons with text - if disabled, the buttons on the website do not show text
Units of distance, volume and weight plus currency - whatever you like, need or know. Note that you'll need to save the options to have the new units displayed in the next three settings:
Avg fuel economy, fuel costs and avg carbon emission - only used for savings calculation, has no impact on optimization.
Speed - the percentage of the normal speed to use in planning. Use 100% for normal speed. If our routes are too fast, e.g. total travel time is too small, use a value below 100%. If our routes are too slow, use a value above 100%.