What is the difference between DNA methylation and histone acetylation?

In DNA methylation, a methyl group is added to the tail of histone proteins. This maintains the histones’ positive charge. The positively charged histone is strongly attracted to the negatively charged DNA, resulting in a more tightly coiled chromatin conformation that prevents transcription factor binding and decreases gene expression.  

In histone acetylation, an acetyl group is added to the tail of histone proteins. This adds a negative charge to the histones, which are otherwise positively charged. These negative charges repel the negatively charged DNA, resulting in a more open chromatin conformation. The more loosely coiled DNA facilitates transcription factor binding and increases gene expression.