Creative Commons copyright licenses allow creators to easily grant copyright permission to their works. Permitted uses could include copying, distributing, editing, re-mixing, or building upon the content. A set of symbols and abbreviations indicate the level of use that is permitted by the creator. While copyright permission is granted through these licenses, the expectation is that the creator will still be properly cited when the work is used.
See License Types and Understanding CC Symbols for more information.
The designations let you know what you can do and how you need to do it. For example, you may be able to share the item with others, as long as you provide proper attribution. Or, you may be able to modify the original and share it, as long as you provide proper attribution and you do not use it for commercial purposes.
The chart below created by shows each of the possible combinations and the rights and restriction associated with them.
Part of How to Attribute Creative Commons Photos by Fotor, licensed CC BY SA 3.0
Note that the author is credited, the license is listed and is linked (you can easily Google the different license types to get the appropriate link). It is also nice to provide a link to the original website where you found the content.
Know what these symbols mean.