"Aamir speaks little."
Translation:आमिर कम बोलता है।
कम literally means 'less'. It can be used for comparisons (eg: मेरे पास उससे कम किताबें हैं - I have fewer books than her) or as 'little'/'not much' (eg: हमारे पास बहुत कम खाना है - We have very little food).
थोड़ा means 'some' or 'a little'. Eg: थोड़ा नमक डालिए- Add some salt.
You can even say 'थोड़ा कम' to say 'a little less'.
Hindi and English use the verb 'to be'/होना a little differently.
In Hindi, है (or its other forms हो/हैं/हूँ) is necessary for almost all present tense sentences. The exceptions are negative sentences with नहीं where है is optional and sentences with चाहिए where it's not used.