Old English also known as Anglo-Saxon. The old English was greatly influenced by many Germanic languages. The major differences between current modern English and old English is that vowels were introduced to the modern English, spellings and pronunciations changed.
Old English used word endings to show whether a noun was the subject or the object of the verb. Modern English mostly uses word order to determine the subject and object in a sentence. Subject comes before verb and verb comes before object in modern English.
Current English is way different than Old English. The big difference is the spelling and the pronounciation of words. Added vowels and syllables in Old English have been shortened in order to make words easier to say and understand in the new and Modern forms of English. Old English is more descriptive and a good example of that is the writings of the legendary playwright William Shakespeare. Modern English is one that is more a universal language and not just one that would you see mainly in the British Isles and Great Britian itself. Words such as ye in Old English would be your or you in Modern English.
There are all kinds of other words in Old English which have been made simplier and more easy to understand in Modern English. There is some kind of underlying similarity between Old English and Modern English and that is that they are both derivatives of the Germanic languages. The big difference is the way words are written and spoken and in some instances have different meanings.