What is the difference between alleles and genes?

Alleles are different variations of genes. A gene is a code of DNA that encodes a protein - together, these proteins form the way we look.

For example, there is a gene in pea plants that encodes height: one allele is tall, the other allele is short.

1. Genes are something we inherit from our parents- alleles determine how they are expressed in an individual.

2. Alleles occur in pairs but there is no such pairing for genes.

3. A pair of alleles produces opposing phenotypes. No such generalization can be assigned to genes.

4. Alleles determine the traits we inherit.

5. The genes we inherit are the same for all humans. However, how these manifest themselves is actually determined by alleles!

Gene is considered as a small stretch of DNA which acts as the molecular unit of heredity. Each gene carries some particular set of instructions necessary for building and maintaining the growth of cells and also passes the information to the offspring.

Allele is an alternative form of a gene situated in a specific locus of a specific gene. Allele is one of the members of a pair of gene that expresses the alternative form of the character which is expressed by the other pair. If the alleles are similar it is called homozygous and if the alleles are different it is heterozygous. 

No, alleles are not part of genes. They are the alternative forms of a gene.

Alleles are the different types of genetic material that code for a specific protein - or gene

In any one locus (position) in a chromosome, the DNA in that region is the code for a protein - a gene.

We often will give them arbitrary names
B - brown eyes
b - blue eyes
(yet another code in that locus yields green eyes)

In the ABO blood group you can have an A or a B allele, or an O
A - A antigen
B - B antigen
O - no antigens

But as we have two sets of chromosomes, that means you can be:
AA or AO -> blood group A
BB or BO -> blood group B
AB (or BA) -> blood group AB
or
OO -> blood group O
Note that if you have an O and a something else, it is the something else that takes precedence (is dominant)
the difference:-
A gene is a section of dna which encodes a protein. one, or more often, many genes are involved in determining physical (phenotypic) characters.

An allele is a version of a gene.

We each inherit two copies of our genes, one form our mother and one form our father, and we all have exactly the same set of genes. the differences between us are caused by different alleles of the same genes.

Each gene can have multiple versions, or alleles (we often talk about two alleles, but there can be many many more). so i have blonde hair, because both my mother and father passed on the blonde hair allele for a hair colour gene. someone with brown hair would have at least one brown hair allele for exactly the same gene (they might have a blonde one as well, but brown is dominant, if you have one, you have brown hair, again we often talk about dominant and recessive alleles, but there are actually lots of ways they can interact).

It gets a lot more complicated then that, often the term locus (plural- loci) is used to refer to a specific section of dna with different possible alleles. this is because how we define a gene can get a bit messy, but the basic principle remains.

So alleles are genes but a different form of it that will produce a different phenotype?

Also bio_man, if alleles are different variations of genes then what are genes?

Think eye color, we all have eye color. Brown would be a variant, therefore that's one allele. Green would be another variant, that's allele two. I mean, nature doesn't work this way, but it's an example.

So bio_man,

So in this case the gene would be the eye colour while the allele would be brown or green?

Yes