Hello
The WMS URL parameters are explained at length in this documentation page.

now , concerning the TIME parameter, this thread will be very useful to you

Does this means the NDVI data is calculated over this time period?

If a time range is specified, the default Priority setting is that NDVI data will be calculated for only the most recent image within the specified time period and not for every image within the time period . You could also specify a different Priority as described in this documentation page

i hope that helps

Best