When you’re transferring ECS from the third-party exchange to the eWallet app - you can spend your ECS and hold it in the eWallet.
This does not apply to other fiat and cryptocurrencies other than ECS until other currencies are supported in the eWallet App.
Otherwise, if you transfer ECS to your exchange account - you can exchange it.
Once you transfer your ECS to the third-party exchange they will be stored in the exchange.
For example, if you convert ECS to EUR the ECS will be traded for the related amount in EUR at the current rate.
The ECS will be sent to the third-party exchange itself (not your wallet) and the corresponding EUR amount will be credited to your third-party exchange account.