Select a option dropdownlist and show values in field , dont load the page .. Javascript o Ajax

Hi Friends,  I need to select a option dropdownlist.... With the selected option look at in preload table may be, Look at record and show values at others field, Not load the page (Javascript , Ajax ??' ).
one thing more, Can I write on dropdownlist and look at into the dropdowlist???

Thank You So Much, Im Sorry my english is very bad......

 
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