First of all, jutsu (術) means "technique", "skill", "method", "trick" or "spell".
A ninjutsu (忍術, lit. "ninja techniques") is one of the three types of jutsu that exist in Naruto. This answer defines it as
a term referring to almost any technique which allows the user to do something that they otherwise would be incapable of doing, including the usage of weapons.
As for "no jutsu" (の術): "no" (の) is a Japanese particle that, in this case, indicates possessive, and jutsu is explained above. That means that the expression "... no Jutsu" means "Technique of ..." or "... Technique".
In that way, Kage Bunshin no Jutsu (影分身の術) is translated to Shadow Clone Technique and Kuchiyose no Jutsu (口寄せの術) is translated to Summoning Technique.
And yes, these two are Ninjutsu.