[CentOS] yum update question

I am running Centos 4.2 x86_64.

When I do "yum update", it shows these packages:

============================================================================
=
 Package                 Arch       Version          Repository        Size
============================================================================
=
Updating:
 compat-openldap         i386       2.1.30-4         update            219 k
 netpbm                  i386       10.25-2.EL4.2    update            110 k
 nss_ldap                i386       226-10           update            1.0 M
 nss_ldap                x86_64     226-10           update            1.1 M
 openldap                i386       2.2.13-4         update            234 k
 openldap                x86_64     2.2.13-4         update            260 k
 openldap-clients        x86_64     2.2.13-4         update            127 k
 openldap-devel          x86_64     2.2.13-4         update            1.4 M
 openssl                 i686       0.9.7a-43.4      update            1.1 M
 openssl                 x86_64     0.9.7a-43.4      update            1.2 M
 openssl-devel           x86_64     0.9.7a-43.4      update            1.6 M
 openssl096b             i386       0.9.6b-22.4      update            614 k
 ruby-libs               i386       1.8.1-7.EL4.2    update            1.5 M
 util-linux              x86_64     2.12a-16.EL4.12  update            1.5 M
 xloadimage              x86_64     4.1-36.RHEL4     update            108 k


Why does it show both the i386 and the x86_64 version of some packages?  Is
this normal?  Should I let it update both of them?

Bowie