I am a young researcher and having problems in understanding certain things. Could you please tell me what does internal region of the ADAM means? dose it by anychance mean the cytoplasmic tail?

There's no special biological meaning, the term "internal region" is just used in its normal natural language context.

There are splice varients of many of the components of the ADAM complex. The description of one ADAM 15 splice varient for example contains:

"This variant (3) lacks an in-frame coding exon compared to variant 6. The resulting isoform (3) lacks an internal region, as compared to the longest isoform 6."

Here internal region just means "internal" as in not at the ends.

Thank you richard.. I appreciate your helping hand.. cheers