NiamH,
Thank you for asking.
In short,
Muslims believe in Jesus(alihi salaam) being born of a miracle birth,and that he ascended to Heaven and that he will descend during the end times to establish the truth and abolish falsehood.
Muslims do not believe in the trinity nor the cruxifiction of Jesus(alaihi salaam) and we do not worship Mary(May Allah be pleased with her),or Jesus(alaihi salaam) or any other humans.
I know you asked for a few sentences as an answer,but as there is a whole chapter in the Quran named after Mary (May Allah be pleased with her)and Jesus(alaihi salaam) is mentioned in the Quran many times,it takes longer than a few sentences to answer your question in full.
Here is some reading material for you.
Mary in the Quran