Binary descriptions:

libx11-6: X11 client-side library
libx11-6-dbgsym: debug symbols for libx11-6
libx11-6-udeb: No summary available for libx11-6-udeb in ubuntu cosmic.
libx11-6-udeb-dbgsym: No summary available for libx11-6-udeb-dbgsym in ubuntu cosmic.
libx11-data: No summary available for libx11-data in ubuntu artful.
libx11-dev: X11 client-side library (development headers)
libx11-doc: No summary available for libx11-doc in ubuntu cosmic.
libx11-xcb-dev: No summary available for libx11-xcb-dev in ubuntu cosmic.
libx11-xcb1: No summary available for libx11-xcb1 in ubuntu cosmic.
libx11-xcb1-dbgsym: No summary available for libx11-xcb1-dbgsym in ubuntu zesty.

Last common version:

2:1.6.4-3