In investments, full replication refers to a type of physically replicated ETF that holds equities in all of the constituents of the benchmark it is designed to track.
For example, a fully replicated ETF which tracks the FTSE 100 (like iShares FTSE 100) would have 100 positions in different equities (as long as there are not more or less constituents in the index, which can occur).
If an ETF only holds a portion of the equities in its benchmark, it is referred to as sample replicated. If it holds none of the equities, but uses derivatives which are linked to those equities, it is synthetically replicated.