There are two basic professionals who provide legal services for legal persons. One is a practicing lawyer (both public and private law firms), and the other is a legal service worker, who exists in judicial administrative organs (mainly grassroots judicial offices). The former can undertake all kinds of cases and undertake entrusted agency; The latter can only undertake the entrusted agency of civil or administrative litigation, and there is no legal guarantee for criminal cases mainly in obtaining evidence or intervening in cases in advance.
For a natural person, a person who does not have the above two qualifications can become an agent ad litem in a civil case, but does not want to appear in court as an agent, and must fulfill the legal procedures of entrusted agency or be the guardian of the principal.