An officer is usualy a person appointed with a specific operational rolse in a busines. Officers generally include President, Secretary and Treasurer but a business can create any officer title role and defined the rights and reponsibilities of the rols.
The LLC laws do not require that a limited liability corporation have LLC officers so they are not strictly required in order to have a valid LLC.
HOWEVER, I alwasy recommend that every LLC have at least the officer roles of President and Secretary. This is because many third parties are going to look for these traditional officer roles when determining who has the authority to enter into business contracts and transactions.
Now, a member of a member managed LLC could sign as a “Member” or “Managing Member” and this would be legally sufficient but the problem is that the other party may be confomfortable with this. They are used to seeing a traditional officer sign contracts- the President in a small company or a Vice President in a larger one.
Even banks, look for Presidents and Treasurers or CFOs to be noted on authority documents. Also, many times a government entity or other party may ask for the Secretary to certify a certain statement or filing.
Instead of having to deal with having to explain your authority structure for your limited liability corporation, just appoint these officers in your LLC Operating Agreement and move on with your business. Believe me, appointing officers is easy and will result in you avoiding delays later.