1.
If you enter into something such as an agreement, discussion, or relationship, you become involved in it. You can also say that two people enter into something. ( FORMAL )
I have not entered into any financial agreements with them...
The United States and Canada may enter into an agreement that would allow easier access to jobs across the border...
No correspondence will be entered into.
PHRASAL VERB : V P n with n , pl-n V n , be V-ed P ( non-recip )
2.
If one thing enters into another, it is a factor in it. ( FORMAL )
There were also other factors that entered into the orchestration.
PHRASAL VERB : V P n