Holy communion and the Lord’s supper aren’t quite interchangeable. What Catholics or Orthodox call Holy Communion or Eucharist is the Body and Blood, Soul and Divinity, of Jesus Christ. What certain ‘high-church’ Anglican/Episcopalians or Lutherans call communion can be anything from a ‘presence’ to a ‘consubstantiation’ (although the latter word is not used so often today) that is not precisely the understanding of the Catholic/Orthodox definition but is also not ‘simply a symbol’. Other protestant groups like Methodists, Baptists, Church of Christ have a Lord’s supper or communion which is purely symbolic, and groups like Friends (Quakers) do not celebrate a communion at all.