The Six of Cups (Six of Ice in the Penguin tarot deck) is a gentle card that represents nostalgia, basking in childhood memories, as well as joy and innocence. The memories that you are fondly remembering do not have to necessarily be from your childhood. It can be from when you were a teenager and from when you were a younger adult. Especially during times that were simpler.
When this card comes up, something from your past is emerging in your life. It could signify a childhood friend will suddenly show up in your life. Perhaps you have been invited to a high school reunion. Whether the memories from high school were happy depends on the other cards in the spread. But it is something from your past that is coming into your life. Usually, this card does represent happy memories from the past, unless it is in reverse.
You may also come across an item that you had as a child that was packed away which will bring back memories. As you may go through your old items in a box.
When the Six of Cups shows up in reverse, it is indicative that you are living in the past and unable to get into the present. This can be due to getting caught up with either positive or negative memories. You may have also lost touch with your inner child which means your life is not fun in any way at all. If you are bogged down by too many responsibilities and have no time for fun, this is what happens and you need a balance.
Astrologically this card is linked to the Sun in Scorpio.