The period (full stop) is the punctuation mark that marks the grammatical and logical end of a sentence.
The main difference comes from its greatest use in English. In Spanish, the period generally signals a pause or separation; the relationship is generally expressed with the comma and the semicolon.
English uses the period before conjunctions, adverbs, or phrases, whereas Spanish opts for a pause that is less marked.
The period is used in English to signal decimals and the comma (NOT the apostrophe) to set off thousands, millions, etc. In Spanish, the practice is the opposite.
It is important to highlight the case of Mexico, as pointed out by Jennifer in the comments, where the system for use of periods in numbers reflects the English system.
