Word order in Esperanto is so called “free word order”. The word order in Esperanto is used to distinguish topic and focus – to express dynamics of the sentence^[39] and not to distinguish between syntactical units (subject and object are distinguished by nominative and accusative). In English, it is necessary to use different means to express the same thing (passive, particles, relative sentence, etc.)^[40]:
Kiun mordis la hundo? – Who was bit by the dog?
La hundo mordis la knabon. (subject – predicate – object) – The dog bit the boy.
Kiu mordis la knabon? – Who bit the boy?
La knabon mordis la hundo. (O – P – S.) – The boy was bit by the dog.
Kion faris la hundo al la knabo? – What did the dog do to the boy?
La hundo la knabon mordis. (P – S – O) – It was biting, what the dog did to the boy.
There are some limitation of this freedom – prepositions have to stand before its noun, adverb has to precede the word it modifies, etc.^[41]

^[39] Topic focus articulation is, simply said, used to distinguish between given and new, between psychological subject and psychological predicate. See Sgall, Hajičová, Panevová: The Meaning of the Sentence in its Semantic and Pragmatic Aspects, Academia, Praha 1986.
^[40] However even in English, certain suggestions of “free word order” can be found: He moved from Boston to Chicago. (Where did he move from Boston?) vs. He moved to Chicago from Boston. (From where did he move to Chicago?); We came to Paris yesterday. (When did we come to Paris?) vs. Yesterday, we came to Paris. (Where did we come yesterday?)
^[41] For more information see PAG §272-274.