Most memories have implicit and explicit aspects, but very early memories, or memories from things experienced when not fully conscious or present may be more implicit than explicit. Implicit memory is also called non-declarative memory, it's memory that exists on a pre conscious, often pre verbal level (which is why some is from before you were able to give things you experienced names or conscious representations). Explicit memory is 'facts and figures' memory - 'knowing what' something is on a level that can be consciously accessed and processed. Implicit memory is 'knowing how' memory, eg how to ride a bike, how something feels, it includes sensory, embodied (somatic) and procedural memories and exists on a deeper less conscious level in the mind. So for example today I went for walk in the park. On an explicit memory level I can remember I went for that walk, the name of the park, how long I took, some people I met, some plants and birds I saw etc - all sorts of facts about it. On an implicit level I have impressions of feelings on my emotions, my senses and my muscles, my body can recall on a somatic level how it felt to walk through the woods, my senses can 'feel' the traces of wind through my hair and over my skin, the cold of the frost, and my emotions can feel how free I felt for a while. And to take me back there on an implicit level might involve something that taps into those memory traces, such as a sound or smell that evokes those memories. Putting them all together enables memory to not just have a factual element but also meaning and emotional/somatic context. But in the brain these elements of memory are stored in different places, some are easier to access than others or require different sorts of 'keys'.