"My brother's violin is on the table."
Translation:El violín de mi hermano está en la mesa.
"es" is a conjugated form of the verb "ser". "está" is a conjugated form of the verb "estar". In English we use "is" in many different ways and Spanish has divided many of those uses among "ser" and "estar". That's a concept you need to accept right now. Words in English that have a number of different meaning may have more than one Spanish word to cover all those meanings. "He is a boy" = "Él es un niño". "Ser" is used here because it is a description. "He is on the table" = "Él está en la mesa". "Estar" here because it is location/position. There are a lot more reasons to use each and exceptions. You can google "ser vs estar" for more help. There is a mnemonic that covers a lot of common situations, but it not a rule or bullet proof.
Ser is Description, Occupation,Characteristic, Time, Origin, Relationship (DOCTOR) and estar is Place, Location, Action, Condition, Emotion(PLACE).
An easier way to remember ser vs. estar, I think, is that ser is used for permanent or long-term conditions, and estar is used for temporary ones.
For example, in this sentence, we use estar because the violin's location is temporary. And if we wanted to say "He is a boy", gender is (usually) permanent, so we would use ser.
Death uses "estar" though. Occupations use "ser" and people change jobs often. Events in time like parties and concerts use "ser" despite seeming to be very temporary things.
In this type of example it is better to realize that estar is used for location. The temporary/permanent guide just confuses things in locational (and many other) examples. Estar would be used to describe the location of the pyramids, for example, or buildings, rivers, and mountains one might naturally think of as permanent, or more permanent than one's occupation at least (which uses ser). Only use the temporary/permanent guide for other situations that are not the easy to remember location or occupation examples. Also, when the temporary/permanent guide fails you (and it will) consider the non-inherent (estar)/inherent quality (ser) guide. It works better for many of the trickier examples.