Young's Analytical Concordance gives several meanings for the Greek words translated 'save', 'to save', 'saving', 'be saved'. There is 'diasozo', to bring safely through, as in Acts 27:43, "...the centurion, willing to save Paul...". It's not that.
Then there is 'sozo', to keep sound, as in John 12:27, "Father, save me from this hour..." and Acts 2:40, "Save yourselves from this untoward generation". It's not that.
Then there is 'sozo' meaning 'to make or keep safe, or sound' as in Acts 15:1, the verse in question. It is that. There is a sense of making something that will last, but the verse itself does not enlarge on being saved. What it does is give us the context in which 'sozo' is being employed.
There were men (Christians known as 'Judaizers') who wanted to insist on Gentile converts to Christianity being circumcised and so oblige themselves to keep all the law of Moses. They were the ones who made that statement - claiming the converts could not be saved unless they were circumcised. The whole 15th chapter needs to be studied to grasp what the debate was about.
In the New Testament, "...the word salvation is a religious term... any healing is a sign of the bestowal of salvation by Jesus. With Jesus, salvation has come to men. ... Man of himself can effect no salvation; even faith, conversion, baptism and constancy in earthly life acquire for him no 'right' to salvation, but are only its necessary presuppositions. Salvation is not restricted to particular groups, as in the OT and in Qumran..." Encyclopedia of Theology, pp.1504-6, article by Ingrid Maisch, Burns & Oates, 1981
That contrasts with the idea of the Judaizers, who were thinking in terms of salvation being for those belonging to the earthly nation of Israel (circumcision being the 'sign' or 'seal' of that covenant.) But Christianity taught salvation from sin (which prevented any drawing close to God) by repentantly putting faith in what Jesus Christ had done to secure salvation for both Jews and Gentiles. Christians find their identity in Christ, not in belonging to any nation - they now belong to the Church, the Bride of Christ, which is spiritual Israel. That is what it means to "be saved" in Christianity (and the Bible New Testament books) but the Judaizers seemed to be having difficulty in grasping that, because they were still thinking in terms of the nation of Israel being God's chosen people - Gentiles ought to be circumcised to belong to it. They had not grasped what it meant to belong to Christ by faith, and so to be saved by Christ.