Trader

Buying and selling of shares based on technical analysis or market trend taking into consideration very short duration like from a single day to couple of days is called trader.
Mostly trading is done throughout the day and wit is called as day trading or intraday trading.
Trader buys and sells the stock and he is not worried about the company’s performance or how good the company is. 

Investor

Buying shares after analyzing the fundamentals of the company and holding them for long term like from couple of months to couple of years is called as Investor.
Investor buys a company only after analyzing its worth.
If the current stock price is available at discount (undervalued) then he buys it for long term prospective