I used to do work out indoor by following those video with proper step but I find that during my 2 months work out I don't see much improvement and so I gave up. After 1 week past I find that I am slightly thinner.
Why is it so? Is this water retention or fat accumulation? I am so confused.

Hi,
Maybe I can shed some light on this as I used to own a gym some time back. The 2 months that you were training was conditioning your muscles. But if you did it every day, your body does not have a chance to develop the muscles. It is called 'overtraining'. When you took the time off, your muscles, which burn fat, had time to recover and grow. The extra muscle increases your metabolism and that in turn burns fat. You may weight nearly the same as before but you will be thinner as muscle takes up less room than fat so you are more compact. For example if you weigh 100 pounds and you are 25% fat you will be larger than someone 100 pounds and only 10 % fat although you both weigh 100 pounds. The fat takes more room than muscle.
To train properly split the week into workout days and rest days. The workout days stimulate muscle growth and fat loss. The rest days are to allow your muscles to recover and grow.
A 2 or 3 days on with a day rest between is a fairly good routine.

Thank you so much Greg