Your mother is your female parent. Mother can mean many things, usually your mother is the lady who gave birth to you and brought you home from the hospital. Sometimes it means the lady who brought you up, if you were adopted.
Some things are together if they are grouped somehow, either because they are near each other or the are doing something related. The three children in the photo are taking a walk together. Often business associates will work together on the same project.
Weather is the word used for the state of the atmosphere in general, such as wind, sunshine, rain and other natural events that come from the sky, for example "it is nice weather today".
An animal's withers is the highest point along their back, generally around their shoulders. Horse's height is measured from the ground to the top of their withers.
A zither is a stringed musical instrument that has a lot of strings like a harp but is flat, not vertical. It is found in Slovenia, Austria, Hungary, some parts of Germany and China.