What does it mean if genes are linked?

Linked genes are genes found on the same chromosome. Chromosomes are distinct 'sections' of DNA, and each gene in an organism has its own place on a chromosome. When genes are linked, it means that alleles (variants of genes) are likely to be inherited together on the same chromosome. Eg, if one person has brown eyes and brown hair, and the genes for eye colour and hair colour are on the same chromosome, that person's children are more likely to inherit both brown eyes and brown hair together on the same chromosome, as opposed to having those alleles split up by crossing over during meiosis (crossing over is when different chromosomes come together and swap sections of DNA with each other, and it mixes up the alleles between the chromosomes).