In the face of major gaps in the fossil record, far-reaching interpretation of fragmentary fossil remains can easily lead to misinterpretation of phylogenetic relationships.
Fossils are the remains of once-living things. They can be plant or animal bodies that have been partially or completely replaced by minerals. They can be impressions that just show the shape of a creature, or tracks left behind by a traveler, or other remnants that testify to the lives of long-gone organisms. Some rare fossils even have original organic soft tissue encased in rock, showing that their organisms couldn't have been dead for millions of years, as evolution claims.
The fossil record provides snapshots of the past that, when assembled, illustrate a panorama of evolutionary change over the past four billion years. The picture may be smudged in places and may have bits missing, but fossil evidence clearly shows that life is old and has changed over time.
See Examples of Evolution at American Geological Institute.