What is the importance of word account in 'Account' assignment elements

Question

Automatic 'account assignment derivation' minimizes the manual effort of entering postings in which the 'account assignment elements' can be entered. The values derived appear as default values that you can overwrite if you wish.
FM account assignment elements, Derivation of FM Account Assignment Elements from CO Acct Assgnmnts.
These are many place where word account assignment elements is used in sap.
what is the importance of word 'Account'. What should we understand if word 'account' assignment element wording is used in FM,CO or FI.

Answer 1

i have tried but no one answers specific question -- What is 'account assignment element'.
its used everywhere as if everyone understands it in every module.
for e.g
FM account assignment elements are not migrated to BCS. Nevertheless, they are crucial to proper migration, since budget data is assigned to these account assignment elements. You have the following options:
·  If you do not want use new FM account assignment elements in BCS, you should proceed as follows:
Migration at fiscal year-end: no specific action is required. See link below.
Migration during the course of a fiscal year: you should carry out the activation of account assignments for BCS and optionally also define your budget structure.
·  If you want to use new FM account assignment elements in BCS, such as the grant or funded program, proceed as follows:
Now if someone is new to SAP what would he understand with word - FM account assignment elements
Like in FI we have GL account and in FM we have Commitment item. Two different nomenclature. Why account assignment element is used freely as If everyone else understands it, I would love to understand that how to interpret word account assignment element differently if used in different module.