Placenta beside womb?

At my 20 week scan my midwife told me my placenta was down beside my womb or in front off my womb... it was last week I can't really remember... what does that mean? I've been feeling movement on and off not much, I was 20w 6days when I went for my scan I'm.now 21w 5 days... how much movement should I be feeling? Could it be cause off my placenta and where it is? Getting abit worried..