wall or ceiling light with clear stick light bulb

E27 stands for the type of the fitting of a lamp. E27 stands for a 27 mm diameter thread. "E" stands for Edison thread. So you always have to put an E27 light bulb in a fixture with an E27 fitting. E27 is the standard in England and most European countries.
The early light bulbs (remember them?) had a similar screw thread.
Be careful though, because there are also countries where E26 bulbs are the norm (for example in the United States).
If you would like to know which standard applies in your country, check out this page.
Check out here the complete collection of E27 light bulbs by zangra.

All light fittings are classified according to their IP value. These IP values (International Protection or Ingress Protection) indicate the degree of protection of the light fitting against dust and moisture. The IP value consists of two digits: the first digit indicates the level of protection against dust; the second, the level of protection against moisture. The higher the IP value, the higher the protection. Check this diagram to see the different existing IP values.
 

What does the IP20 value mean on this light fitting?

IP20 means that the light fitting:
2: is protected against the intrusion of solid particles with a dimension greater than 12.5 millimetres.
0: has no protection against water penetration.

This light fitting can be installed indoors, but not in wet areas.
It is not recommended to install this light fitting outdoors.

A device with an IP20 value is not protected against dust or moisture. A light fitting marked IP20 may have holes to prevent overheating. However, the lamp is protected against contact with objects larger than 12.5 mm, such as a hand or finger.
This model is suitable for indoor use, but not outdoors.

This lamp is fixed to the ceiling/wall with a metal bracket. The screws that serve to attach the bracket to the lamp are included. The screws used to attach the bracket to the ceiling/wall are not included because the type of screw depends on the material of the wall or ceiling (concrete, brick, plasterboard, wood).