An alcohol is not a hydrocarbon. This is because it also contains, in its structure, an Oxygen atom. One of the Carbon atoms must be bonded to Hydroxide($\text{OH}$). Some examples of an alcohols are:
Butanol $\text{C}4\text{H}{9}\text{OH}$
Ethanol $\text{C}2\text{H}{5}\text{OH}$
The general formula for an alcohol is:$^1$
$$ \text{C}n\text{H}{2n+2}\text{O or }\text{C}n\text{H}{2n+1}\text{OH} $$
The second one is preferable but both are correct.$^1$
A Carboxylic Acid contains two Oxygen atoms. One of the Carbon atoms are bonded with hydroxide($\text{OH}$) and the same Carbon atom is double bonded with one Oxygen atom.$^1$
Some examples are:
Ethanoic Acid ($\text{C}4\text{H}{4}\text{O}_2$)
Butanoic Acid ($\text{C}4\text{H}{8}\text{O}_2$)
The general formula of a Carboxylic Acid is: $^1$
$$ \text{C}n\text{H}{2n}\text{O}_2 $$
Esters are a derived compound. Esters are formed by reacting an alcohol and a carboxylic acid.$^2$
This kind of reaction is called esterification, where the reactants are an alcohol and a carboxylic acid and the products are an ester and water molecules.$^2$
The second carbon atom in the ester should be double bonded with oxygen. The name of the ester is methyl ethanoate
The general form of an ester is RCOOR’. Where R and R’ are any organic combining group.$^2$
Naming an ester is simple.$^3$ Name the carboxylic acid(RCOOH) and replace the ending with -ate. For example, ethanoic acid becomes ethanoate. The second step is to name the R’ group. In general, R’ will be an alkyl(derived from Alkane, one hydrogen atom will be removed). For example, in the above diagram the alkyl group has one carbon. There for it is named as methyl. The full name is then methylethonate$^2$