EDSS is the Expanded Disability Status Scale, which is the most widely used method of measuring MS-related disability. It goes for 0 to 10, with 0 being no detectable impairment, and 10 being death (it’s very rare to die as a result of MS, but the scale has to include all shades of this hugely variable disease).
The scale has been criticised as focusing disproprtionately on walking, and not so much on other things people with MS might have wrong with them - but it’s still the benchmark most neuros use.
DMT just means Disease Modifying Therapy (sometimes also referred to as Disease Modifying Drug, DMD). In most cases, but not always, the recommended drug will be some kind of injectable.
Check out a website called MSDecisions for more info about the most widely prescribed DMTs. Results so far suggest they are all much of a muchness in terms of effectiveness, which is why you’ll probably be invited to choose one, rather than have it foisted on you. But they still have subtle pros and cons you might want to consider. The choice depends mainly on your own personal priorities - there’s no right or wrong.
And of course, you don’t have to have them at all - but if you’re considering not, that will be something to discuss with your consultant.
Hope this helps,