What does this paragraph in the ps man page mean?

Question

I could not understand the following description:

   a               Lift the BSD-style "only yourself" restriction, which is
                   imposed upon the set of all processes when some BSD-style
                   (without "-") options are used or when the ps personality
                   setting is BSD-like. The set of processes selected in this
                   manner is in addition to the set of processes selected by
                   other means. An alternate description is that this option
                   causes ps to list all processes with a terminal (tty), or
                   to list all processes when used together with the x
                   option.

Only thing I could understand is the An alternate description is xxxx. What does Lift the BSD-style "only yourself" restriction and other sentences mean?

Answer 1

By default, the BSD version of ps (and, by extension, Linux's ps when it is treated as a BSD ps by passing it BSD-style options or by setting the PS_PERSONALITY or CMD_ENV environment variable to bsd) lists only the processes owned by the user running ps.

The a argument lifts that restriction and will show processes regardless of their owner.